The present invention relates to earth working equipment. More particularly this invention relates to a boom arm pivoting linkage mechanism which is used on such an earth working device.
The invention finds particular application in the cleaning and maintaining of road shoulders or berms where vegetation needs to be cut or soil or debris need to be moved, and will be described with reference thereto. However, it should be appreciated that the invention also finds application in other boom arm environments.
Heretofore, road maintenance equipment, such as mowing apparatus, has been connected with prime movers such as tractors in various ways. Articulated boom assemblies have been found to be particularly advantageous for supporting mowing apparatus on tractors or the like. Such a boom assembly includes a plurality of arms, a first of which is pivotally connected with tee tractor and a second of which is pivotally connected between the mowing apparatus and the first arm. Hydraulic cylinders are provided to control the angular orientation of the first arm relative to the tractor and the second arm relative to the first arm.
One particular known mechanism employs a pair of hydraulic cylinders in order to enable a pivoting motion of a boom arm, to which a rotary cutting mechanism was secured, over substantially 180.degree. of motion. However, this mechanism was not tied in with a breakaway system so that if an obstruction is encountered by, e.g., an earth working device secured to the free end of a boom arm, the boom assembly could pivot the earth working device away from the obstruction before any damage would be caused to either the earth working device or the boom mechanism. In addition, the known mechanism is fairly large in size and is adapted only for use on a rear end of a construction vehicle.
It would be advantageous to have a linkage mechanism which would allow a substantially 180.degree. pivoting motion of a boom arm around a pivot axis, which includes an overload protection circuit and a means responsive to a movement of a piston for selectively disabling the overload protection circuit.
Accordingly, it has been considered desirable to develop a new and improved linkage mechanism for a pivotable boom arm which would overcome the foregoing difficulties and others and meet the above stated needs while providing better and more advantageous overall results.